The major drawback of a low velocity projectile device like a bow is the parabolic trajectory of the projectile, requiring accurate distance and angle estimation, particularly at hunting or combat distances. For example, using a bow at a distance of 35 yards, a range estimation error of as few as two or three yards can cause a complete miss on a deer-size target. To further complicate matters, a downhill shot, for example one from an elevated tree stand or window, causes the projectile to fly higher than would be the case in a horizontal shot at the same distance. The same applies to an uphill shot. Skilled bowhunters develop their range-estimation ability through dedicated practice in field conditions, some shooting “instinctively”, i.e. without the use of sights or even conscious range-estimation. This requires long hours of practice under varying conditions which is not practical for many hunters. In addition, to develop a high level of skills for combat applications of a low velocity projectile, a significant number of training rounds must be expended at a high cost in both training material and time.
Archery has been practiced by many nations for millennia. The principle of guiding an arrow accurately to a target has been used to provide sustenance, for sport, and in some cultures has attained a spiritual quality. The basic principles of archery have remained largely unchanged with respect to today's practice of archery.
Part of archery's allure is the difficulty required in attaining effective archery shooting skills. Many hours of discipline and practice are required to accurately hit a still target. Still more discipline and skill are required to hit a target in motion. Many archers who are proficient at hitting a still target are ultimately unsuccessful when shooting at a moving target. The moving target requires that the archer mentally compute a ballistic solution that includes an estimation of a “lead” or an aim point slightly ahead of the moving target so that an arrow fired at a point in space reaches this point in space the same instant in time as the target. The leading skill is desirable to effectively hunt and it must be practiced for the archer to become proficient in the leading skill. Much of this skill involves the archer developing a “sense” or skill at target motion estimation determining target speed and combining this “sense” with a familiarity with a bow and arrow. The velocity of an arrow is dependent upon the draw weight of the bow which the archer is shooting. The archer must know the velocity of the arrow at a given draw of the bow, or as in developing the leading skill, the archer must become very familiar with the archer's own equipment such that all variables in the ballistic calculation are “sensed” or known by the archer. These “senses” can only be acquired with substantial practice and integration of the archer's physical and mental processes. This integration of mind and body is responsible for much of the enjoyment experienced by seasoned archers.
For simplicity, our discussion will focus on hunting applications although applicable to any low velocity projectile, such as the M-203 grenade launcher and other devices.
Simple sights have long been known for use with archery bows and other low velocity projectile weapons, i.e. those with an exit velocity below approximately 1000 fps. They range from simple pin markers to peep sights, to vertically aligned series of horizontal pins mounted in a generally annular frame to protect the pins. These latter multi-pin sights have proliferated in the last few years, especially in the hunting arena, where the distance to a target or target animal can vary as much as from 10 to 60 yards. In the bow hunting situation, the trajectory of an arrow must be accurately predicted if an archer is to have any confidence in accurate shot placement. Since the typical range to a target may vary substantially, it is critical that a good estimate of the distance for a particular shot be known with some degree of accuracy. The archer typically has to use a remote measuring device or physically measure the distance to an anticipated target location from the archer's tree stand, blind, or other shooting location. Alternatively he or she must simply guess as to the appropriate distance in order to compensate for the effects of gravity on an arrow in flight to the target. In the past, there have been few tools to aid the shooter in this endeavor.
One such tool has been a multiple position sight which can be a pin sight in the case of archery or a leaf sight in the case of a grenade launcher. Normal multi-pin sights simply have several brass aiming pins which stick out horizontally from a vertical frame mounted in front of the hand grip on the bow. Each pin provides an aiming point from the shooters eye position useful for a particular target distance. The archer visually estimates the appropriate range and then sights to the target using the appropriate aiming pin corresponding to that range. Recently an enhancement to the multi-pin sight has been introduced. This sight has light gathering fiber optic filaments which provide a self powered illuminated dot that the archer sees at the end of each aiming pin. These fiber optic multiple pin sights have greatly improved the utility of such sights in low light or low contrast lighting situations.
Hand-held range-finding instruments are available and present one solution to the problem, but are awkward to use and require extra movement at a time when any movement is undesirable. Crude range estimation devices for hunting use are available, relying on spaced stadia wires subtending a set angle, which brackets an “average” deer's chest at certain specified distances, but these are not widely used owing to wide variations in body size within and between species. Neither aid corrects for differences in elevation between the target and the archer.
Sophisticated bow-mounted aids are known. These fall into two main classes: the first comprises sights incorporating optical range-finders which measure the line-of-sight distance but not the angle of inclination or declination to the target; the second class relies on measurement of the angle of declination from an elevated shooting position but not the line-of-sight distance to the target.
Aids of this first type include U.S. Pat. No. 3,136,697 dated Dec. 29, 1964, claiming an optical range-finder based on a dual spaced mirror device and coupled sighting element; U.S. Pat. No. 2,788,701, dated Apr. 16, 1957, claiming the use of a multi-mirror device; U.S. Pat. No. 4,555,856, dated Dec. 3, 1985, claiming a third adjusting compensating mirror and cam-coupled sight pin; U.S. Pat. No. 4,646,444, dated Mar. 3, 1987, claiming a self-indicating planar/parabolic mirror combination; and U.S. Pat. No. 4,178,693 claiming a two-mirror, split image bowsight incorporating a cam-controlled alignment mechanism. All of these devices are accurate only when the shot is approximately level, and where one or more sight components are customized to the specific shooter, bow, and projectile. For example, the inventions described in the U.S. Pat. Nos. 4,178,693 and 4,555,856 must be customized by highly sophisticated mathematical modeling techniques or by trial and error. The invention described in the U.S. Pat. No. 4,646,444 is provided with means of adjustment relying on the deflection of a flexible, variable thickness mirror-however it does not have precise horizontal aiming point providing suitable alignment with a particular spot on a nondescript target such as a deer.
The second class of aids includes U.S. Pat. No. 4,120,096 dated October 1978, claiming a pivoted sight whose position relative to the sight picture is appropriately elevated as the bow is tilted from the horizontal; U.S. Pat. No. 4,796,364, dated Jan. 10, 1989, claiming a dual sight comprising a pendulum sight for shooting from an elevated position and a multi-pin sight for use on level ground, each of which can be secured out of the archer's line-of-sight when not in use; U.S. Pat. No. 4,711,036, dated Dec. 8, 1987, claiming two versions of a pendulum-actuated sight; U.S. Pat. No. 4,325,190, dated Apr. 20, 1982 claiming a plurality of sights selectively illuminated according to the angle of declination of the bow via an electronic circuit incorporating a plurality of switches; and U.S. Pat. No. 4,400,887, dated Aug. 30, 1983, claiming a plurality of sights and a means for selectively causing one pin to be readily distinguishable from the others according to the angle of declination of the bow, via a pendulum-mounted colored lens positioned to selectively interrupt multiple fiber-optic cables. None of these devices serves as a range-finding aid on level or upwardly sloping ground, nor do they function properly where the elevation of the archer relative to the target is unknown (for example where the elevated stand is situated above sloping ground) or where the archer is significantly above or below the restricted height range for which the sight is calibrated. Furthermore, except for the precalibrated multi-pin sights of the U.S. Pat. Nos. 4,325,190 and 4,400,887, all of these aids provide the same sight correction for all bow/shooter/projectile combinations. In practice, the vast majority of bow hunters shoot and hope for the best, resulting in a higher incidence of poor hits and lost game than would be the case if an accurate range-finding sight were used. Indeed, increasing controversy over the humaneness of the bow as a hunting weapon in the hands of the average hunter mandates the development of such a device.
Laser rangefinders are available and well known in the art (such as described in U.S. Pat. Nos. 6,108,071, 5,379,676, and 6,073,352 incorporated herein by reference) however they are separate devices that require separate movement and action to initiate in a time when seconds count. In addition, once the laser distance is determined, a visual estimate is still required to interpolate between fixed pin positions.
To address the accuracy of range estimating, laser rangefinders have been developed and marketed by a variety of companies, including Laser Atlanta, Leica, Bushnell and Nikon among others. These rangefinders enable the determination of the distance to the target, however the archer still has to choose which of several sighting pins to align with the target based on the distance displayed or manually adjust the pin using the technique shown in U.S. Pat. No. 6,494,604 based on the distance determined so that the aiming pin represents the correct solution to the ballistics equation. For example, if the archer has preset the pins to distances of 10, 20, 30, 40, and 50 yards, the archer would choose the pin closest to the displayed target distance. In one model, the Bushnell laser rangefinder is integral with the multiple pin sight. The entire sight may be removed from the bow and used as a hand held distance measurement device. In another example, the rangefinder is modular and may be removed from the bowsight for use as a hand held distance measuring device.
One of the major disadvantages with the use of a rangefinder is that it only indicates the range when aimed directly (i.e., via line of sight) at the target. Thus, after the range is determined, the archer must raise the bow such that the appropriate distance pin of the bow sight is aligned with the target. The archer may choose the incorrect pin with which to aim at the target, resulting in a missed shot. Another disadvantage is that the rangefinder alone does not automatically compensate or adjust for the angle from which the shot is being fired. Another disadvantage is the rangefinder alone is very difficult to use with moving targets, especially targets running away from the archer or shooter or running toward the archer or shooter. Hunters often fire an arrow from an elevated position and in some instances fire upward at an angle. Hunting birds may require shooting at an angle at a moving target which could be very difficult. There is also a need to record images of the target animal and several devices have been developed to include a camera on a bow, however none of those devices are fully integrated with a sight device as described herein.
Therefore there is a need for an integrated bow sight that automatically compensates for the angle from which the projectile or arrow is being fired
Therefore there is a need for a versatile archery or low velocity sight which automatically tells the archer or shooter where to aim when aiming at a particular target so as to avoid the potential for missing the target. Because projectile velocity is critical to solving the ballistic equation, knowledge of arrow velocity is needed. This velocity can be measured prior to a hunt and stored, however changes in temperature and humidity and other factors can changes the arrow velocity, therefore there is a need to predict arrow velocity based on conditions instant to the projectile launch and a need to measure actual arrow velocity as the arrow is fired and a need to store and update specific arrow velocities in each arrow so that minute differences in arrow speed can be included in the ballistic algorithm